I just checked and it does almost the same thing as the preview button (if not the same) another advantage the preview button has is that it saves your post in the draft in case you accidentally delete your post. they both have drafts.
the whole tool offers almost identical possibilities and I have not found any upgrade compared to the already existing one that comes with the forum... plus what makes this even more complicated due to switching between tabs, there is always the additional possibility of an error in copy/paste.
I haven't tried it, maybe it's more practical for those who write on mobile devices. Certainly an interesting tool, but without excessive utility value.
